1. Field of the Invention
The present invention relates to a silicon carbide epitaxial substrate, a method of manufacturing the silicon carbide epitaxial substrate, a method of manufacturing a silicon carbide semiconductor device, a silicon carbide growth device, and a silicon carbide growth device member. In particular, the present invention relates to a silicon carbide epitaxial substrate for a silicon carbide semiconductor device required to have a high breakdown voltage, a method of manufacturing the silicon carbide epitaxial substrate, a method of manufacturing the silicon carbide semiconductor device, a silicon carbide growth device, and a silicon carbide growth device member.
2. Description of the Background Art
Epitaxial growth of a compound semiconductor such as silicon carbide on a substrate needs to be performed by reacting a treatment gas (source material gas or the like) under a high temperature.
Conventionally, in an epitaxial growth device used for epitaxial growth of silicon carbide, a material capable of being inductively heated and having a high heat resistance is employed for members, such as a heat generator and a susceptor, that form a growth chamber. An example of such a material is a carbon material.
Japanese Patent Laying-Open No. 2006-028625 describes a CVD device in which a film member having a high etching resistance for a carrier gas is formed on a susceptor made of a carbon material. Also described therein is a CVD device in which the nitrogen concentration in the film member covering the susceptor is made very low.
However, the inventors of the present application have found that even though the nitrogen concentration in the film member covering the susceptor is made low as described in Japanese Patent Laying-Open No. 2006-028625, it may be difficult to sufficiently reduce the background concentration of nitrogen in a silicon carbide epitaxial layer obtained through epitaxial growth and having good surface quality. It should be noted that the term “background concentration” in the present specification refers to a nitrogen concentration in an epitaxial layer obtained by performing epitaxial growth without using a dopant gas.
Specifically, the inventors of the present application have found that in order to attain good surface quality in a main surface of a silicon carbide epitaxial substrate, it is necessary to perform epitaxial growth under a predetermined growth condition. Also, the inventors of the present application have found that under the above-described growth condition, nitrogen is likely to be captured in the silicon carbide epitaxial substrate and it is difficult to sufficiently reduce the background concentration of nitrogen in the obtained silicon carbide epitaxial layer using the technique of Japanese Patent Laying-Open No. 2006-028625. Moreover, the inventors of the present application have found that the in-plane distribution of the background concentration of nitrogen is large in the main surface of the conventional silicon carbide epitaxial substrate. It has been confirmed that a large in-plane distribution of background concentration in a silicon carbide epitaxial layer will result in a large in-plane distribution of impurity concentration (nitrogen concentration) in the silicon carbide epitaxial layer even when doped with nitrogen as an impurity during epitaxial growth.
The present invention has been made to solve the foregoing problem. The present invention has a main object to provide: a silicon carbide epitaxial substrate having good surface quality and having a sufficiently reduced background concentration of nitrogen; a method of manufacturing such a silicon carbide epitaxial substrate; a method of manufacturing a silicon carbide semiconductor device; and a silicon carbide growth device and a silicon carbide growth device member, each of which allowing for manufacturing of a silicon carbide epitaxial substrate that has good surface quality, that has a sufficiently reduced background concentration of nitrogen, and that has a uniform in-plane distribution of nitrogen concentration.